The invention relates to the field of lifting attachments for small power units such as skid steer loaders, Dingoes(copyright), small tractors and xe2x80x9cfour wheelerxe2x80x9d ATVs. More particularly it relates to a forklift attachment with rolling stabilizers for skid steer loaders and the like.
A wide variety of versatile motorized prime movers are used in the construction, maintenance, and grounds upkeep industries. These include skid steer loaders, light tractors, garden tractors, xe2x80x9cfour wheelerxe2x80x9d all terrain vehicles, and many other compact power units. Skid steer loaders, in particular, are widely employed for a variety of material handling, earth moving and transportation tasks.
In general, these devices are favored for their compact size, maneuverability and ability to utilize many attachments to accomplish a variety of jobs. The need for these units to be readily transported, generally on a trailer pulled by a pickup truck or other small truck, limits their overall weight. In addition, their high maneuverability is a consequence of their short wheelbase and overall length.
Counterweights may be used at the opposite end of the power unit from load lifting attachments to balance the vehicle. In order to balance a massive load, a long moment arm or a heavy counterweight must be used. Consequently, the ability of these units to lift loads is limited by the need to keep the overall length and weight of the power unit relatively small.
For example, skid steer loaders used in landscaping may be fitted with fork attachments to move pallets supporting rolls of sod or concrete landscaping materials. An example of such a device is disclosed in U.S. Pat. No. 3,458,069 to Wickberg et al. Fully loaded pallets of landscaping or construction materials are commonly heavy enough to exceed the capacity of the machine to lift them with out raising the rear wheels from the ground. This forces the contractor to use only partially loaded pallets; to employ other machinery at significant expense; or to redistribute at least some of the materials by hand labor. All of these options are inefficient and costly.
In addition to lifting loads, compact power units are used to move lifted loads to a variety of locations over many types of terrain. For example, in the construction and landscaping industries, loads are often moved over unpaved surfaces, up, down and across slopes and over generally uneven ground. In order to maintain stability of the vehicles as they currently exist, loads must be kept low and close to the center of gravity of the vehicle. Tall, heavy loads in combination with a slope or uneven ground can cause compact vehicles to be dangerously unstable or even to overturn.
The versatility of these already flexible machines would be even greater if their lifting capacity were increased without significantly increasing their weight or reducing maneuverability. Particularly the ability to lift and transport pallets of heavy materials safely over uneven terrain is beneficial. An increase in the height to which loads can be lifted would also be helpful. Additionally, it would be desirable that the stability of the loader, the lifted load and attachment be maximized.
The present invention increases the lifting capacity of the power unit it is attached to dramatically beyond that of the power unit alone. It makes practical the safe, stable transport of heavy loads over uneven terrain that cannot be accomplished by the power unit alone. In addition, the invention allows lifting to a greater height than the loader alone is capable of.
The present invention is a rolling stabilizer lift attachment that is designed to be manufactured as a product family. Different size ranges of the invention may be manufactured to fulfill different user requirements, the needs of different industries and different pricing categories. The rolling stabilizer lift is adjustable to varying working conditions, providing maximum load stability when desired and offering a compact configuration for operating in restricted spaces.
The lift attachment comprises five major components: a mounting plate, a lifting mast, a right rolling stabilizer, a left rolling stabilizer, and lifting forks or other load engaging apparatus. The rolling stabilizer lift may be adapted to attach to a large variety of power units so long as the power unit is sufficiently powerful to move the intended load.
The mounting plate may be adapted to accommodate coupling to many different types of power equipment. The mounting plate may be attached to the rest of the assembly by a freely rotating lateral pivot, in order to allow the rolling stabilizers to remain in full contact with the ground despite irregularity of the terrain. The rotation of the pivot may be limited to prevent the rolling stabilizer load from overturning if the ground is dramatically irregular and to allow the attachment to be raised from the ground safely. Additionally, the rotation of the pivot may be restricted from free rotation by a braking mechanism. Some applications may benefit from a non-pivoting attachment.
The right and left rolling stabilizers or outriggers each comprise a width adjustable support and a swiveling, caster mounted support wheel and tire. The rolling stabilizers are similar aside from being opposite handed. The rolling stabilizers place the load bearing caster wheels somewhat ahead of and to the sides of the lifting mast.
The lifting mast is generally centered between the rolling stabilizers and provides a means for lifting loads. The lifting mast may lift the load via lifting forks however, bale spears, buckets and other load engaging devices may also be utilized. In most cases, the lifting mast will be actuated hydraulically although other actuation approaches may be used. If the power unit connected to the rolling stabilizer lift has a hydraulic power supply, it may be used to operate the lifting mast or a self contained power supply unit may be incorporated on the lift attachment itself. It is preferred that the lifting mast be configured to lift to a height of at least eight feet.
In connecting the hydraulic system of the rolling stabilizer lift to the hydraulic pressure supply of the power unit a safety issue arises. It is possible for the operator to disconnect the two systems, intentionally or inadvertently, while a load is still supported by the lifting mast. The power unit may also become disabled or suffer power loss. Upon disconnection of the pressure supply, or if the accidental severance of a hydraulic connection should occur, the load could drop causing damage or injury. Additionally, the release of hydraulic fluid under pressure may be hazardous. A safety device to prevent these occurrences is thus a desirable part of the invention.
The safety device comprises a manifold combining a pilot operated check valve with a pressure relief valve. The resulting integrated valve system requires hydraulic pressure to be maintained in the circuit to actuate lift cylinder lowering. If hydraulic pressure is lost, the pilot operated check valve closes holding the lift cylinder in its then current position. The manifold reduces the need for plumbing between individual hydraulic components.
In use, the rolling stabilizer lift attachment is attached to a power unit via the mounting plate. The width of separation of the stabilizers may be adjusted as appropriate for the job at hand. The power unit may be driven as usual allowing for the added space requirements of the lift attachment. Power units that have independent lift modules may lift the attachment off the ground to facilitate relocation of the rolling stabilizer lift when the unit is not loaded, for example, to place the rolling stabilizer lift on a truck or trailer for transport.